Production of lubricant-grade molybdenite from byproduct concentrates of porphyry copper ores

ABSTRACT

Lubricant-grade molybdenite is produced from byproduct molybdenite flotation concentrates of porphyry copper ores by a sequence of purification steps which include controlled grinding to liberate contaminant minerals and to flatten the molybdenite, followed by a flotation step for the selective recovery of the so-flattened molybdenite. The grinding is controlled to soften impact and minimize duration of the grinding period.

limited States Patent REGULAR MOLYBDENITE RODUCT CONCENTRATE OM COP ER SULFIDE- MGLYBDENITE GENERAL CONCENTRATE DEPRESSAN REAGENT FOR IRON SULFIDES Castillo lFelo. 29, 11972 [54] PRUDUCTHQN 01F LUBRICANT-GRADE 2,112,299 3/1938 Mills .....75/2 MULYBDENTTE FROM BYPRODUCT 2,606,660 8/1952 Klepetko ..209/162 CONCENTRATES 0F PORPHYIRY FOREIGN PATENTS OR APPLICATIONS COPPER URES 7 454,695 2/1949 Canada ..75/2 [72] Inventor: Cecilio O. Castillo, Hurley, N. Mex.

73 Ass-l nee: Kenna C C N Primary Examiner-Winston A. Douglas l g York 1? upper orpora ew AssismntExaminer-Peter D. Rosenberg Aztorney--John L. Sniado, Mallinckrodt and Mallinckrodt, P. d: Apr. 4, 1969 H. Mallinckrodt and Phillip A. Mallincikrodt 21 A l. N 13 l 1 p 0 8 57 ABSTRACT [52] USCLW 241/20 75/2 209/164 Lubricant-grade molybdenite is produced from byproduct [51] lnt'cl 303d B03d 1/14 molybdenite flotation concentrates of porphyry copper ores [58] Field of 5 209/l62 164 by a sequence of purification steps which include controlled 3 5 241/14 grinding to liberate contaminant minerals and to flatten the molybdenite, followed by a flotation step for the selective [56] References Cited recovery of the so-flattened molybdenite. The grinding is controlled to soften impact and minimize duration of the grinding UNITED STATES PATENTS P l,84l,438 1/1932 Greenawalt ..75/2 SClaims, 1 Drawing Figure TO REGULAR MOLYBDENlTE PLANT DEPRESSANT REAGENT FOR COPP R AND IRON $3 LFlDES FOR COPPE AND IRON SULFIDES LUBRICANT GRADE MOLYBDENlTE PRODUCT (98% M05 040% msol) Patented Feb. 29, 1972 REGULAR MOLYBDENITE BY-PRODUCT CONCENTRATE FROM COPPER SULFIDE- MOLYBDENITE GENERAL CONCENTRATE DEPRESSANT REAGENT FOR COPPER AND BQN SULFTDES TO REGULAR MOLYBDENITE PLANT DEPRESSANT REAGENT FOR COPPER AND IRON SULFIDES 20\ 35 FJ U TO REGULAR MOLYBDENITE PL ANT DEPRESSANT REAGENT FOR COPPER AND IRON SULFIDES ill nun a LUBRICANT GRADE MOLYBDENITE PRODUCT (98% sol) M082 0.40% in INVENTOR CECILJO O. CASTILLO ATTORNEYS PRODUCTION 01F LUBRICANT-GRADE MOLYBDENITE FROM BYIPIRODUCT CONCENTRATES OF PORIPI-IYRY COPPER ORES BACKGROUND OF THE INVENTION Field The invention has to do with the metallurgical upgrading of byproduct molybdenite flotation concentrates that are commonly derived by copper producers from general flotation concentrates resulting from the milling of low-grade porphyry copper ores.

State of the Art A variety of upgrading procedures are customarily employed in the particular art concerned to produce a molybdenite concentrate of acceptable commercial grade for the production of molybdic oxide and related products. Lubricant-grade molybdenite, however, requires such a high degree of purity (98% M05 0.40% insol) that heretofore no significant success has been attained by porphyry copper ore proces sors in the practical production of such product; it has been left to the processors of relatively high-grade molybdenum ore to supply market demands.

Objectives In the making of the present invention it was a principal purpose to provide an economically attractive process for the production of a lubricant-grade molybdenite product from the relatively impure molybdenite concentrates customarily obtained by primary copper producers as a byproduct from general copper sulfide-molybdenite flotation concentrates. Another purpose was, by so doing, to improve operation of the conventional molybdenite recovery plant customarily utilized by such copper producers.

SUMMARY OF THE INVENTION The present process may utilize several well-known metallurgical processing techniques in combination with a special grinding procedure and a subsequent flotation step for the selective floating of the molybdenite and recovery thereof as an exceptionally high-purity froth concentrate.

Thus, a byproduct molybdenite concentrate, which usually though not necessarily will be of commercially acceptable grade for the production of molybdic oxide, but below lubricant grade, may be passed sequentially through a number of processing steps, such as sizing, dewatering, steaming, and again dewatering, before being subjected to light impact grinding for only so long as fractures the gangue minerals and merely flattens the molybdenite. Grinding for too long a time even with light impact, as in small diameter ball mill using a light load of lightweight balls, will tend to fracture the flattened molybdenite and reduce the effectiveness of the process.

The grinding not only frees most of the molybdenite from other minerals which impair its floatability, but, by reshaping the molybdenite mineral grains into flat flakes or platelets, it removes previously absorbed reagents and produces fresh new broad surfaces that apparently are favorable for floatability. A molybdenite froth concentrate of high purity is obtained in a subsequent flotation step using reagents specific to molybdenite.

THE DRAWING The single FIGURE of the drawing constitutes a flowsheet schematically illustrating a combination of processing steps presently contemplated as the best mode of carrying out the invention in actual practice.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT As illustrated, it is presently preferred to pass the porphyry copper molybdenite concentrate in its slurry form into a vessel 10, from where it is fed under the control of a pump 11 to a cyclone I2 for separation of coarse and fine particles. The

fines fraction (usually 3l5-mesh or finer) is passed to a thickener 13, and the thickened solids are passed by means of a diaphragm pump 14 to a conditioning vessel 15 for steaming to remove most of the surface-adherent reagents carried over from the earlier general flotation treatment of the porphyry copper ore concerned and to deactivate so far as possible the gangue minerals. The conditioned molybdenite concentrate is then passed to a second thickener 16 for dewatering prior to being passed to the special grinding stage of the process.

It should be noted that the insoluble and copper and iron mineral content of the feed concentrate will be considerably reduced by the sizing step and that, although cycloning is a preferred way of carrying out the sizing, screening or other size classification procedures can be employed for the purpose. Also, in addition to dewatering, the thickening operations serves to store the feed material for batch operation of the system, to exercise a limited washing function in eliminating carryover reagents, to cool the mineral material following steaming, and to regulate the feed to the remainder of the circuit.

In specifying the steaming step, it is assumed that a xanthate was utilized as a collector reagent for the copper minerals in the initial treatment of the porphyry copper ore by flotation to obtain the general flotation concentrate from which the molybdenite flotation concentrate, constituting the feed in the present process, was derived. If a different reagent or other conditioning procedures were employed, it may not be desirable to utilize the steaming step or it may be advisable to substitute other steps therefore, all as will be apparent to those skilled in the art.

The thickened solids from the second thickener are passed, under the control of a pump 17, to a special ball mill 18 adapted to exercise only light impact. Thus, such ball mill is advantageously of smaller diameter than would normally be utilized in a grinding circuit of the type concerned and advantageously contains fewer and lighter grinding balls. On the other hand, the grinding equipment may be a suitable pebble mill or some other type of apparatus that will fracture the insoluble gangue while merely flattening the molybdenite to produce flakes or platelets. It is impractical to attempt to specify in greater detail the characteristics of the apparatus or procedures employed for this grinding step, but the grinding is easily carried out and controlled as required for any given feed material by observing the nature of the produce resulting therefrom. Grinding time is important from the standpoint of producing the desire flakes of molybdenite with a minimum of fracturing thereof by prolonged subjection to impact, even though such impact be relatively light.

The discharge from this grinding step of the process is passed to a conditioning tank 19 along with the conventional reagent for depressing copper and iron sulfides and, after appropriate conditioning in conventional manner, is passed to rougher and first cleaning cells of a flotation circuit 20, which is of conventional type for the floating of the molybdenite while depressing the copper and iron sulfides.

As illustrated, the molybdenite float concentrate is passed through additional processing for further cleaning. This includes dewatering in a thickener 21, grinding as before described in a special ball mill 22, conditioning in a conditioner 23, and flotation in second and third cleaning cells of a flotation circuit 24.

The tailings from flotation circuit 20 and flotation circuit 24 of the present process represent a regular molybdenite concentrate. These tailings are consolidated, as shown, and are passed to the regular molybdenite plant.

To guard against the possibility that any fine insoluble gangue remains therein, the final molybdenite froth concentrate from flotation circuit 24 of the present process is desirably passed to a vessel 25, from where it is fed under the control of a pump 26 to a cyclone 27 for a final size separation treatment, the separated fines being run into the stream of consolidated tailings that are returned to the regular molybdenite plant.

' cant'grade molybdenite.

The coarse fraction from the initial sizing of the feed molybdenite concentrate is advantageously continuously passed from the cyclone 12 through a separate processing circuit comprising a regular ball mill 31, conditioner 32, and flotation cells 33. This coarse fraction contains most of the impurities present in the feed concentrate. The tailings from the flotation circuit 33 are peculiarly adapted for upgrading in the regular molybdenite plant. If returned as a circulating load to the plant from which it originally came, this molybdenite ore material is especially adapted to subsequent regular flotation treatment by reason of the treatment received during the present process. Thus, insoluble gangue minerals are liberated from previous attachments to the molybdenite by reason of the grinding and are deactivated in preparation for the regular flotation procedure. The molybdenite froth concentrate of flotation circuit 33 goes to the first thickener 13 by way of a vessel 34 and pump 35.

Typical of comparative tests performed in accordance with the above are the following: v I

A quantity of a byproduct molybdenite concentrate from the regular molybdenite plant of the Chino Mines Division of Kennecott Copper Company was sized by screening through a standard ZOO-mesh screen. The oversize, containing about 3 percent of the copper, 40 percent of the iron, 55 percent of the insolubles, and 12 percent of the molybdenite, in the sample was rejected. The fines were split into four parts and processed in parallel in accordance with the flowsheet. Each part contained about 1,000 grams of solids assaying for copper, iron, insol, and molybdenite as indicated in a table of results appearing herebelow, and each was dewatered to about 60 percent solids, steamed for 30 minutes, dewatered again to about 60 percent solids, subjected to light-impact grinding for 30 minutes to fracture gangue minerals and place the molybdenite in flake form with clean polished surfaces, repulped to a density of percent solids. conditioned, and subjected to flotation with the recovery of lubrication-grade molybdenite (98.8% MoS 0.32% insol).

A single processing stage was employed for each test, but the flotation step included a rougher and three cleaning stages. These were carried out in accordance with the follow ing table:

Head assays and results of these tests utilizing the process of the invention were given in the following table:

TABLE ll Head tests (after sizing) Product tests 1.13 1.14 1.14 .25 .24 .25 .24 2.39 2.30 2.30 .16 .i6 .I6 .15 11.04 ll.l2 |l.ll .30 .29 .36 .32 82.3 82.0 82.9 98.5 98.8 98.9 99.2

MOS, 30. I 27.6 22.l

TABLE ill I Reg MOS; conc. tests Circulating load tests dist. MoS9. 54.3 57.8 62.8 69.8 15.6 14.6 15.1 14.2

Whereas specific procedures are illustrated and described, it should be realized that other procedures could be employed 1 within the purview of the disclosed inventive concepts.

What I claim is:

l. A process for the production of lubricant-grade molybdenite from high purity molybdenite concentrates derived from general copper sulfide-molybdenite flotation concentrates as a byproduct of the recovery of copper from porphyry copper ores, said process including the steps of sub ectlng such molybdenite concentrate to impact gnndmg sufficiently light in character and short in duration to merely flatten the molybdenite and form it into flakes;

subjecting the so-treated molybdenite concentrate to flotation for collecting the flake molybdenite into a froth concentrate; recovering the said froth concentrate of flake molybdenite;

removing any'significant quantities of impurities that may I remain in said concentrate of flake molybdenite; and preparing the resulting flake molybdenite as a lubricant grade product. 2. A process in accordance with claim 1, wherein the molybdenite concentrate feed to the process is preliminarily treated for quantity reduction of gangue impurities.

3. A process in accordance with claim 2, wherein the preliminary treatment comprises sizing the molybdenite concentrate feed, and passing only the fines fraction resulting therefrom to the impact grinding step.

4. A process in accordance with claim 3, wherein before 

2. A process in accordance with claim 1, wherein the molybdenite concentrate feed to the process is preliminarily treated for quantity reduction of gangue impurities.
 3. A process in accordance with claim 2, wherein the preliminary treatment comprises sizing the molybdenite concentrate feed, and passing only the fines fraction resulting therefrom to the impact grinding step.
 4. A process in accordance with claim 3, wherein before passing the fines fraction to the impact grinding step, said fraction is treated for removal of carryover collector reagents from mineral particle surfaces.
 5. A process in accordance with claim 4, wherein the coarse fraction is subjected to grinding and conditioning in preparation for flotation and is then subjected to flotation for the recovery of molybdenite contained thereby. 